1. Field of the Invention
The present invention generally relates to an apparatus and a method of controlling the flow of hydrocarbons into and/or out of a string of tubing disposed in a wellbore. More particularly, the invention relates to an apparatus and a method of controlling the flow of hydrocarbons into a string of tubing that can be regulated remotely.
2. Description of the Related Art
FIG. 1 shows a cross-sectional view of a typical hydrocarbon well 10. The well 10 includes a vertical wellbore 12 and, thereafter, using some means of directional drilling like a diverter, a horizontal wellbore 14. The horizontal wellbore 14 is used to more completely and effectively reached formations bearing oil or other hydrocarbons. In FIG. 1, the vertical wellbore 12 has a casing 16 disposed therein while the horizontal wellbore 14 has no casing disposed therein.
After the wellbore 12 is formed and lined with casing 16, a string of production tubing 18 is run into the well 10 to provide a pathway for hydrocarbons to the surface of the well 10. The well 10 oftentimes has multiple hydrocarbon bearing formations, such as oil bearing formations 20, 21, 22 and/or gas bearing formations 24. Typically, packers 26 are used to isolate one formation from another. The production tubing 18 includes sections of wellscreen 28 comprising a perforated inner pipe (not shown) surrounded by a screen. The purpose of the wellscreen is to allow inflow of hydrocarbons into the production tubing 18 while blocking the flow of unwanted material. To recover hydrocarbons from a formation where there is casing 16 disposed in the wellbore, such as at formations 20 and 21, perforations 30 are formed in the casing 16 and in the formation to allow the hydrocarbons to enter the wellscreen 28 through the casing 16.
In open hole wellbores, to prevent the collapse of the formation around the wellscreen 28, a gravel packing operation is performed. Gravel packing involves filling the annular area 32 between the wellscreen 28 and the wellbore 12, 14 with sized particles having a large enough particle size such that the fluid will flow through the sized particles and into the wellscreen 28. The sized particles also act as an additional filtering layer along with the wellscreen 28.
FIG. 2 shows a cross-section view of a typical gravel packing operation in a horizontal wellbore 14. The sized particles are pumped at high pressures down the tubing 18 as a slurry 34 of sand, gravel, and liquid. The slurry 34 is directed into the annular area 32 by a cross-over tool 36. A second tubing (not shown) is run into the inner diameter of the production tubing 18 in order to block the apertures of the perforated inner pipe of the wellscreen 28. The second tubing prevents the liquid of the slurry 34 from flowing into the wellscreen 28. Thus, the slurry can be directed along the entire length of the wellscreen 28. As the slurry 34 fills the annular area 32, the liquid portion is circulated back to the surface of the well through tubing 18, causing the sand/gravel to become tightly packed around the wellscreen 28.
Referring back to FIG. 1, because the hydrocarbon bearing formations can be hundreds of feet across, horizontal wellbores 14 are sometimes equipped with long sections of wellscreen 28. One problem with the use of these long sections of wellscreen 28 is that a higher fluid flow into the wellscreen 28 may occur at a heel 40 of the wellscreen 28 than at a toe 42 of the wellscreen 28. Over time, this may result in a “coning” effect in which fluid in the formation tends to migrate toward the heel 40 of the wellscreen 28, decreasing the efficiency of production over the length of the wellscreen 28. The “conning” effect is illustrated by a perforated line 44 which shows that water from a formation bearing water 46 may be pulled through the wellscreen 28 and into the tubing 18. The production of water can be detrimental to wellbore operations as it decreases the production of oil and must be separated and disposed of at the surface of the well 10.
In an attempt to address this problem, various potential solutions have been developed. One example is a device which incorporates a helical channel as a restrictor element in the inflow control mechanism of the device. The helical channel surrounds the inner bore of the device and restricts fluid to impose a more equal distribution of fluid along the entire horizontal wellbore. However, such an apparatus can only be adjusted at the well surface and thereafter, cannot be re-adjusted to account for dynamic changes in fluid pressure once the device is inserted into a wellbore. Therefore, an operator must make assumptions as to the well conditions and pressure differentials that will be encountered in the reservoir and preset the helical channel tolerances according to the assumptions. Erroneous data used to predict conditions and changes in the fluid dynamics during downhole use can render the device ineffective.
In another attempt to address this problem, one method injects gas from a separate wellbore to urge the oil in the formation in the direction of the production wellbore. However, the injection gas itself tends to enter parts of the production wellbore as the oil from the formation is depleted. In these instances, the gas is drawn to the heel of the horizontal wellbore by the same pressure differential acting upon the oil. Producing injection gas in a hydrocarbon well is undesirable and it would be advantageous to prevent the migration of injection gas into the wellbore.
In still another attempt to address this problem, a self-adjusting flow control apparatus has been utilized. The flow control apparatus self-adjusts based upon the pressure in the annular space in the wellbore. The flow control apparatus, however, cannot be selectively adjusted in a closed or open position remotely from the surface of the well.
Therefore there is a need for an apparatus and a method which controls the flow of fluid into a wellbore. There is a further need for an apparatus and method which controls the flow of fluid into a production tubing string which may be remotely regulated from the surface of the well while the apparatus is in use.